The present invention relates to an apparatus and method for automatically tracking a moving object, so that the object is always positioned in front of the lens of a camera by controlling the camera.
In a general video conferencing system, a video telephone and a monitoring system, a camera picks up an image of an object which is transformed as a video signal. The picked-up video signal is transmitted or stored in a recording medium. As each of the above systems were introduced, the camera was fixed to the main body of each system. Thus, when an object was not positioned in front of the camera due to its movement, a user manually adjusted the position of the system body itself or the camera itself, in order to direct the camera toward the object so that the latter was positioned in front of the camera lens allowing its image to be picked up.
However, when a user moves during dialog in the video conferencing system or video telephone, the above manual repositioning of the camera causes the user to be conscious of the camera. The user must also directly adjust the camera while watching the monitor, which causes inconvenience during use of the systems.
To solve these problems, a conventional apparatus includes a camera driving device for rotating a camera in a horizontal or vertical direction, and a motion detector for detecting a motion of the object. The camera automatically rotates in the direction of the detected motion. The degree of rotation also corresponds to the degree of detected motion. The camera driving device includes two motors for rotating the camera in a horizontal or vertical direction. The motion detector detects a motion vector of the object from sequential unit images obtained by a picture tube, using a well-known block matching algorithm (BMA). The apparatus generates motor drive signals having the direction and magnitude which correspond to the detected motion vector of the object, and controls the camera so that the object is positioned in front of the camera lens. Thus, the method for automatically adjusting the camera according to the movement of the object reduces the inconvenience of using the video conferencing and telephone systems.
However, in the above automatic method, the camera cannot track the object when the object is beyond the range in which the camera can be rotated in a horizontal or vertical direction.
To solve the above problems, it is an object of the present invention to provide a method for expanding an object search region of a camera using a zooming operation. A conventional automatic camera control method is performed when the camera is within a camera rotation range, and a zooming operation is performed to adjust the object search region when the object is beyond the camera""s rotational range.
It is another object of the present invention to provide an apparatus embodying the above method.
To accomplish the above object of the present invention, there is provided a method for automatically tracking a moving object by controlling a camera, the automatic object tracking method comprising the steps of: (a) comparing sequential unit images with each other, detecting a motion vector of the object, generating camera control signals corresponding to the detected motion vector, and controlling the camera to track the moving object; (b) checking whether the camera reaches the limit of rotation range of the camera; and (c) performing a zooming operation in the direction of expanding an object search region of the camera until the object is positioned within a predetermined effective region whenever it is determined that the camera reaches the limit of the rotation range of the camera.
To accomplish another object of the present invention, there is also provided an apparatus for automatically tracking a moving object, the automatic tracking apparatus comprising:
a camera including a zoom lens and an automatic focus lens, for converting an image of the object input through the lenses into an electrical signal; a camera support unit including a camera driver on which the camera is mounted, for rotating the camera around a first axis and a second axis perpendicular to the first axis and a rotation limit detector for detecting whether the camera reaches one of the limits of the rotation range of each direction and outputting a detection signal if the camera reaches a limit of the rotation range; a first controller for comparing a current unit image output from the camera with a previous unit image, detecting a motion vector of the object, and controlling the camera drive means so that the camera moves in the direction and degree in correspondence to the motion vector; and a second controller for adjusting the zoom lens in the direction of expanding an object search region of the camera whenever a detection signal, indicating that the camera has reached a limit of the rotation range, is activated, thereby allowing the camera to track the moving object, and adjusting an automatic focusing lens using a luminance component of the image received in the camera.